关键词: 石墨烯, 甲醇氧化, PtCo复合催化剂, 电沉积, 抗CO中毒

Direct methanol fuel cells are excellent power sources due to their high energy density, low pollutant emission and easy handling. However, commercial applications are limited by the high cost related to noble metal catalysts. Recent findings have proved that appropriate catalyst support, which improves the utilization of the noble metals in great depth, may be one breakthrough. Graphene nanosheet (GNS), a new two-dimensional carbon material with a single (or a few) atomic thickness, as the combination of its high surface area, high conductivity and unique graphitized basal plane structure, has recently attracted an enormous amount of interest from both theoretical and experimental scientists. It has been proved that catalysts supported on GNSs show improved activity than those supported on carbon black. Furthermore, alloying Pt with other metal is widely approved as a practical method to relieve the CO-poisoning of the catalyst, which can be ascribed to both a bi-functional mechanism and a ligand (electronic) effect. In this experiment, PtCo/graphene (GN) composite catalysts were synthesized on an indium tin oxide (ITO) substrate by the potentiostatic method. Catalyst samples were characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDX) and electrochemical methods. SEM results showed that the addition of graphene could enhance the dispersion of the catalytic particles and reduce the particle size, especially when the molar ratio of Pt and Co is 1:2.93, the particles had the smallest size and the best dispersion. Electrochemical tests demonstrated that graphene as the catalytic support could improve the CO-tolerance of the catalysts, which was determined by the outstanding electric conductivity and rich oxygen-containing species of graphene, resulting in good performance for electrocatalytic methanol oxidation. Furthermore, owing to the special electronic effect of Co, its addition also influenced the catalytic activity. It was found that when the molar ratio of Pt and Co was 1:2.93, the composite catalyst exhibited the most excellent catalytic performance for electrocatalytic methanol oxidation with the forward anodic peak current density of 662 A·g_pt^-1and the I_f/I_b of 2.34 which was nearly 1.8 times that of the traditional PtCo/C catalyst (I_f/I_b=1.32).

Key words: graphene, methanol oxidation, PtCo composite catalyst, electrodeposition, CO-tolerance